A solar battery is known as a simple and clean energy source without emitting toxic substances. Exposed to sunlight, it operates as a DC power supply and outputs DC power. A power conditioner for photovoltaic power generation system serves to convert DC power generated by a solar battery into AC power to supply the power to a general AC load or to an existing commercial power system. Since the solar battery is installed at a location receiving sunlight, such as on a roof of a house, the power conditioner for photovoltaic power generation system is also installed outdoors in many cases.
To protect such an outdoor-installed power conditioner from external factors such as rainwater, dust or impact, an enclosure is used to house the outdoor-installed power conditioner. FIG. 22 is a perspective view showing an enclosure for a conventional outdoor-installed power conditioner.
Referring to FIG. 22, an enclosure 201 for an outdoor-installed power conditioner includes an outer case 202 housing the power conditioner and a lid 203. Outer case 202 is open at its one side face, and lid 203 is used to close the opening. Lid 203 is fastened to outer case 202 from the opening front side of outer case 202, with a plurality of screws 204.
FIG. 23 is a front view showing the outdoor-installed power conditioner housed in the outer case in FIG. 22. Referring to FIG. 23, outer case 202 houses an input/output terminal pad 207 for connecting interconnections from a commercial power system 209 and a DC power supply 208, and a power converter 206 for converting DC power into AC power. When carrying out electric work for connecting the interconnections from DC power supply 208 and commercial power system 209, screws 204 are loosened to remove lid 203 from outer case 202, and then the work is carried out.
However, in enclosure 201 for the conventional outdoor-installed power conditioner, the number of screws 204 used for fastening should be increased to achieve closer contact between outer case 202 and lid 203 to prevent rainwater or the like from infiltrating into the inside from a gap between the attachment faces of outer case 202 and lid 203. Such an increase in the number of screws 204 causes problems of an increase in manufacturing cost and a decrease in workability of attaching lid 203 to outer case 202.
In addition, in enclosure 201 for the outdoor-installed power conditioner, since lid 203 is fastened with screws 204 from the front side of enclosure 201, the appearance of enclosure 201 is spoiled.
Further, when lid 203 is removed from outer case 202 for carrying out the work for connecting the interconnections, power converter 206 will become exposed since lid 203 has the same size as that of the opening of outer case 202. If the work for connecting the interconnections is carried out in such a situation, the worker may accidentally touch or damage power converter 206. Furthermore, a foreign matter such as dust is more likely to enter the inside of outer case 202 during the work for connecting the interconnections.
The following is another conventional outdoor-installed power conditioner. FIG. 24 is a perspective view showing an appearance of the conventional outdoor-installed power conditioner.
Referring to FIG. 24, an outdoor-installed power conditioner 301 includes an outer case 302, a lid 304 closing an opening provided on the front side of outer case 302, and a mounting plate 303. Outdoor-installed power conditioner 301 is installed outdoors with mounting plate 303 mounted on an outer wall of a building. An intake vent 305 is provided in a bottom face 302a of outer case 302, and an exhaust vent 306 is provided in a rear face 302b of outer case 302. Intake vent 305 is provided with rectangular holes arranged in a plurality of rows. Mounting plate 303 is provided on rear face 302b of outer case 302 in communication with exhaust vent 306, and a slit portion 307 is provided in its side face.
FIG. 25 is a cross-sectional view along the line XXV—XXV in FIG. 24. Referring to FIG. 25, a power converter 335 converting DC power output from a solar battery or the like into AC power is provided within outer case 302. A power element 314, which is the most heat generating element in power converter 335, is provided so as to contact a surface of a heat sink 311 attached on bottom face 302a of outer case 302.
In an upper part of outer case 302, a fan supporting portion 317 is fastened on rear face 302b of outer case 302 with a screw 318. A fan 316 is fastened to fan supporting portion 317 with screws 315a and 315b so as to be located between fan supporting portion 317 and heat sink 311. A rotary blade is provided within fan 316, blowing air in a direction indicated by an arrow 331. The air introduced by fan 316 into fan supporting portion 317 flows in a direction indicated by an arrow 332 and is exhausted from exhaust vent 306. Fan 316 is provided such that the direction indicated by arrow 331 and the direction indicated by arrow 332 form an angle β of 90°.
Rear face 302b of outer case 302 is provided with an upper hook portion 320, a middle hook portion 333, and a lower screw-fastened portion 319. Outer case 302 is fixed to mounting plate 303 by locking these portions to facing portions of mounting plate 303 and fastening them with screws.
FIG. 26 is a cross-sectional view along the line XXVI—XXVI in FIG. 24. With reference to FIG. 26, a cooling structure of conventional outdoor-installed power conditioner 301 will now be described.
Referring to FIG. 26, outside cool air is taken in from intake vent 305 provided in bottom face 302a of outer case 302 into heat sink 311 by operating a rotary blade 329 within fan 316. The inside of heat sink 311 is divided into a plurality of chambers by blade portions extending vertically, and the air passes through each chamber formed in this manner. Since the heat generated at power element 314 has been conducted to the blade portions of heat sink 311, the air passes in contact with the blade portions within heat sink 311 and removes the heat of the blade portions. As a result, power converter 335 is cooled down.
The air heated by heat exchange with the blade portions within heat sink 311 moves to an upper part of heat sink 311, passes through an aperture 323 provided in a bottom face of fan 316 and an aperture 324 provided in a bottom face of fan supporting portion 317, and is blown into fan supporting portion 317. The air blown into fan supporting portion 317 first strikes against an upper face of fan supporting portion 317. About 50 percent of the air striking against the upper face flows in a direction toward exhaust vent 306 indicated by an arrow 326, and the remaining 50 percent flows in a direction opposite to exhaust vent 306 indicated by an arrow 327 and circulates within fan supporting portion 317.
The air exhausted from exhaust vent 306 passes through a space formed by mounting plate 303 and is exhausted from slit portion 307. Since the air flows in a direction indicated by an arrow 328 in this case, it first strikes against mounting plate 303 and is exhausted from slit portion 307 to the outside of outdoor-installed power conditioner 301.
In the cooling structure actively taking in outside cool air to air-cool the inside with the air as described above, air used for heat exchange should readily be exhausted outside the conditioner. Further, the enclosure for an outdoor-installed power conditioner should protect the electronics provided in the enclosure from external factors such as rainwater or dust. Furthermore, since the fan taking in outside air is driven by a motor and is a consumable, it is to be replaced at the end of its life. Thus, maintenance of the fan should be performed easily.
However, in conventional outdoor-installed power conditioner 301, the direction in which the air blown out by fan 316 flows is relatively perpendicular to the direction in which the air exhausted from exhaust vent 306 flows, and thus the air taken in by fan 316 is not efficiently exhausted to the outside of outer case 302. Further, also within mounting plate 303, the air first strikes against mounting plate 303, and thus is not efficiently exhausted from slit portion 307 to the outside of outdoor-installed power conditioner 301. Due to the above-mentioned reasons, efficiency for cooling power converter 335 in heat sink 311 may be reduced, leading to the possibility of an increase in the temperature of power converter 335 not being suppressed sufficiently.
Further, if opening areas of intake vent 305 and exhaust vent 306 are enlarged in an attempt to take in more air to the inside of outer case 302 and improve cooling efficiency, rainwater may infiltrate into outer case 302 from intake vent 305 and exhaust vent 306 during a rainstorm or the like.
Furthermore, when fan 316 is to be removed from outer case 302 for its maintenance, interference of heat sink 311 and power converter 335 when removing screws 315a and 315b is troublesome. Therefore, firstly, screw 318 should be unfastened to remove fan supporting portion 317 from outer case 302, and then screws 315a and 315b should be unfastened to remove fan 316 from fan supporting portion 317. Performing such a work takes time and effort, degrading workability during the maintenance of fan 316.
Still another conventional outdoor-installed power conditioner is disclosed in Japanese Patent Laying-Open No. 11-122949. The power conditioner includes an enclosure, and an exhaust vent is provided in a rear face of the enclosure. Cooling wind cooling a power supply apparatus within the enclosure is exhausted from the exhaust vent. The enclosure is mounted via a wall-hung plate attached on an outer wall surface. Here, a spacer piece is provided between the wall-hung plate and the rear face of the enclosure, which forms a gap between the exhaust vent and the outer wall surface to prevent the exhaust vent from being blocked by the outer wall.
In the above power conditioner, the cooling wind is exhausted from the exhaust vent provided in the rear face of the enclosure. Since the periphery of the exhaust vent is open to the outside, rainwater may easily infiltrate from the exhaust vent into the enclosure. Further, when trash such as fallen leaves accumulates between the rear face of the enclosure and the outer wall surface, the exhaust vent may be clogged by the trash.